Fuse-plug.



No. 804,741.' PATENTED NOV. 14, 1905. P. Q. LAWRENCE. FUSE PLUG.

APPLICATION FILED FEB.8, 1905.

www www l @M I UNITED STATES PATENT OFFICE.

PEROY Q. LAVRENOE, OF REVERE, MASSACHUSETTS, ASSIGNOR OF ONE- HALF TO LOUIS GREENBURG, OF BOSTON, MASSACHUSETTS.

FUSE-PLUG.

Specication of Letters Patent.

Patented Nov. 14, 1905.

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Be it known that I, PERCY Q. LAWRENCE, a citizen of the United States, residing at Revere, county of Suffolk, and State of Massachusetts, have invented an Improvement in Fuse-Plugs, of which the following description, in connection with the accompanying drawings, is a speciiication, like numerals on the drawings representing like parts.

This invention relates to fuse-plugs, and has for its object to provide a novel fuse-plug which is so constructed that the condition of the fuse therein, whether intact or blown, can be determined by a glance at the plug. In most fuse-plugs now commonly used there is no way of visually detecting whether the fuse is blown or not, and it is often a matter of considerable labor to locate the blown fuse in a number of fuse-plugs. lith my improvement, however, if the fuse in any one of a number of fuse-plugs blows it is possible to locate the blown fuse by a glance at the plugs.

My improved fuse-plug has a cavity therei in in which is located the fuse, and one wall of the cavity is provided with a detachable telltale which is dislodged from the wall by the force of the gas generated when the fuse blows. This telltale is positioned so as to be visible at all times, and the condition of the fuse within the fuse-plug may therefore be determined by a mere glance of the telltale to see whether it is in place or has been blown out of place.

In the drawings, Figure 1 is a vertical sectional view through a fuse-plug embodying my invention. Fig. 2 is a section on the line :r at, Fig. 1. Fig. 3 is a top plan view of the plug with the cap and disk removed and Fig.

4 is a section of the blanks from which the disk, hereinafter described, is formed.

My invention may be embodied in fuseplugs of various shapes, and in the drawings I have illustrated one of the common forms of fuse-plugs, which comprises a plug 1, 4of porcelain, glass, or other insulating material, said plug having the portion 3 of reduced diameter and a cavity 5, within which the fuse 6 is located, one end of said fuse being attached to a terminal 7 at the end of the plug and the other to an annular terminal 8, surrounding the portion 3, having the reduced diameter, said annular terminal being in the form of a metallic band which is provided with screwthreads, so that the plug can be screwed into the socket in which the plug is used. The fuse 6 extends through an aperture 9 in the side of the plug in order that it may be soldered or otherwise attached to the terminal 8, said aperture being filled with plaster-ofparis, as usual. This form of fuse-plug isone of common construction, and the parts thus far described form no part of my invention. In applying my invention to this type of plug I place a disk 10 of any suitable material on top thereof, which disk has an opening or aperture therein in which is detachably supported a telltale 13. This telltale is arranged so that it will be dislodged from the disk 10 by the force of the gas generated in the cavity 5 when the fuse 6 blows, and therefore by observing the position of the telltale-that is, whether it is in place in the disk or has been dislodged therefrom-the condition of the fuse can be ascertained. I find it most practical to make the telltale of just the size to `lit the aperture of the disk 10, so that said telltale will be frictionally held in place in the disk, but my invention is not limited to this particular way of detachably securing a telltale in place.

`When a fuse blows, there is more or less flame and gas generated, and in order to direct this gas and flame which issues from the aperture in the disk 10 backwardly or in a direction to cause no injury I have covered the end of the plug with a cap 11, which is spaced from the disk 1() to afford a chamber orspace 14, and have formed in the periphery of the enlarged portion of the plug one or more longitudinal grooves or passages 15, which connect with the chamber 14, and through which passages the gas and flame may escape. In order to permit the telltale 13 to be seen at all times, I have provided the cap 11 with a sight-opening 12, which will preferably be covered with some suitable transparent material 16, such as glass or mica. The cap 11 is held spaced from the disk 10 by struts 17, which are interposed between said disk and the transparent sheet 16, as seen in Fig. 1, and for convenience of construction I prefer to make these struts as integral parts of the disk, said disk being made from a blank such as shown in Fig. 4, which has the ears or projections 17 extending therefrom, so that by bending said projections up at right angles to the disk the struts shown in Fig. 1 are formed. The struts 17 perform two functions: First,

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they serve to hold the transparent sheet 16 against the cap 1 1, and, second, they serve to hold the disk 10 against the plug. Any other construction by which these results are accomplished may be used, however, without departing from the invention.

The cap 11 is secured to the plug in any suitable way, either by sorewthreading it thereto or by spinning or bending the edge 18 of the flange of the cap around the shoulder 19.

From the above it will be observed that my invention comprises ay plug having a cavity within which the fuse is located and a telltale detachably supported in or secured to one wall of said cavity, whereby when the Jfuse blows theiorce of' the gas generated dislodges the telltale. My invention also comprises a plug so constructed that the telltale is visible at all times, whereby the condition of the fuse maybe determined by merely noting the condition o'f the telltale. The telltale may be provided with a luminous surface, so that it can be readily seen in the dark.

While I have shown in the drawings only one type of plug, yet it will be understood that my invention can be embodied in plugs of other shapes and construction, provided they have the removablysupported telltale which is dislodged from its seat by the eX- plosion when the fuse blows.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. A fuse-plug having a cavity, a Jfuse within the cavity, an apertured plate or disk seated on the end of the plug and closing said cavity, a telltale detachably held in the aperture of said plate or disk, a cap secured to the end of the plug, said cap having an aperture, a transparent member covering said aperture, and struts interposed between the apertured disk Aor plate and the transparent member, said struts operating to space the cap from the disk and also to hold the transparent member in place.

2. A fuse-plug having a cavity, a fuse within the cavity, terminals exterior to the plug to which said fuse is connected, an apertured disk seated against the end of the plug and closing the cavity, a telltale detachably held in said aperture and a cap carried by the plug and provided with a transparent portion through which the telltale is visible.

3. A -fuse-plug provided with a cavity, a fuse within the cavity, an apertured plate or disk seated against the end of the plug and closing said cavity, a telltale detachably held in the aperture of said plate, a cap secured to the plug and inclosing said plate but spaced therefrom, said cap having a transparent portion through which the telltale is visible, and passages for the escape of gas formed in said plug and communicating with the space between the cap and plate.

1. A fuse-plug having a portion of reduced diameter, said plug having a cavity therein, a fuse within the cavity, a plate or disk engaging the top of the plug and closing said cavity, said plate having an aperture, a telltale removably supported in said aperture, a cap supported by the plug, said cap being spaced from the plate and provided with a transparent portion through which the telltale is visible, and longitudinal grooves or passages in the portion of the plug having the larger diameter, said grooves communicating with the space between the cap and disk or plate.

5. A fuse-plug having a cavity theren,one wall of said cavity being provided with an aperture, and a luminous visible telltale 'filling said aperture and detachably supported therein.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

PERCY Q. LAIRENCE. Witnesses Louis C. SMITH, LoUrs GREENBURG. 

